The Allison B500 has some sort of fluid level check capability built in. If you hit the downshift and upshift arrows on the pad while in neutral with the engine running, it will show 'O L' and then on mine it slowly counted down from 8 to 1 and then flashed 'O h' on the display. This fluid level check is supposed to be better than the dipstick.

Any idea how exactly the display is interpreted? It appears if it counts all the way down to one that I either am 1 quart low and n ot low at all, but I am not sure on that.

BTW, I learned about this from rv.net. Someone posted that their Class A with a Allison 3000 series tranny had this feature, so I had to try it on my B500. (Allison 3000 series and the B500 are basically the same tranny.)

Ok, well I got my Allison transmission families mixed up. Regardless, both the B500 and the 3000 series appear to have the fluid level check functionality and I'm trying to learn more about it.

For the heck of it, can someone try holding down the upshift and downshift buttons on a HT series tranny with a touchpad and see if that model displays 'O L' on the LCD display? (I believe there are HT series trannies with the touchpad.)

As was posted previously, the engine needs to be running in neutral, low idle and the transmission needs to be at normal operating temperature.

Depress both arrows at once. A countdown will begin, and at the end of the countdown the fluid level will be displayed. The display will tell if you are low or if the oil level is "O k " Refer to the book to decipher the code shown because it doesn't read intuitively.